1. Field of the Invention
The present invention relates to an artificial respiration apparatus and in particular, to a high-frequency oscillation respiration apparatus.
2. Description of the Related Art
As shown in FIG. 16, in a conventional high-frequency oscillation aspiration apparatus 200, an inhale gas containing a high-concentration oxygen is supplied from an oxygen supply source 201 to flow through a fluid path system having a three-way branching pipe 202 for branching to a patient X and an exhale side. The inhale gas is urged by a high-frequency (3 to 15 Hz) oscillating air pressure generated by an oscillating air pressure urging unit 203 to flow with a flow rate of 10 to 30 [1/min] at a normal mode and 60 [1/min] at maximum for supplying oxygen to lungs of the patient X. Here, the average pressure applied to the lungs of the patient is controlled according to an open degree of a rubber valve of an inhale valve 204 provided at an outlet of the inhale gas. The average pressure is normally set so as to maintain 5 to 15 [cm H2O] (490 to 1470 [Pa]) (hereinafter, the pressure values represent values added to the atmospheric pressure).
Explanation will be given on a principle of oxygen supply in the high-frequency oscillation artificial respiration apparatus 200. Firstly, when an inhale gas to be supplied to a patient is urged by a high-frequency oscillation oscillating air pressure, the pressure amplitude of the inhale gas causes a small-amount ventilation (gas exchange like convection) with respect to the gas containing carbon dioxide to be exhaled (hereinafter, referred to as an exhale gas). Simultaneously with this, vibration of the inhale gas causes a diffusion movement, which causes the inhale gas to intrude into the lungs via an in-trachea tube 207 and the exhale gas to be transferred out of the lungs (up to the mouth of the patient). A subsequent exhale gas portion performs the aforementioned ventilation and urges the exhale gas, which has been transferred out of the lungs, to be sent to the outlet. Thus, it is possible to maintain a constant oxygen concentration in the lungs of the patient.
Japanese Utility Model Publication (examined) 2-7569 discloses a high-frequency oscillation artificial respiration apparatus using a mechanical piston and electrical speaker vibration as an oscillating air pressure urging unit. However, these methods provide only a small amplitude of oscillating air pressure for urging the inhale gas and cannot perform a sufficient ventilation for lungs of a grow-up and have been used only for new-born babies.
In the high-frequency oscillation artificial respiration apparatus as shown in FIG. 16, which is disclosed in Japanese Patent Nos. 2798255, 2798256, and 2798257, a blower 205 and a rotary valve 206 are used as the oscillating air pressure urging unit 203 so as to improve the high-frequency oscillation oscillation.
Moreover, in the aforementioned high-frequency oscillation artificial respiration apparatus 200, the user (doctor) can set the following basic parameters according to the state of the patient: (1) inner pressure (5 to 15 [cmH2O] (490 to 1470 [Pa]) of a flow path from the oxygen supply source to the patient x; (2) a ventilation amount per oscillation cycle with respect to the lungs of the patient (hereinafter, referred to as one ventilation amount against the lungs of the patient; more specifically, several to several hundreds of [ml] according to the weight of the patient); and (3) ventilation frequency (3 to 15 [Hz]) of the oscillating air pressure. In addition to these, there are accompanying parameters: an inhale gas supply amount and an inhale gas oxygen concentration of the inhale gas sent to the patient. According to the state of the patient, the aforementioned basic parameters are controlled as follows to control respiration.
(1) When oxidation is required, i.e., when it is necessary to increase the partial pressure of oxygen (PaO2) in the artery blood of the patient X, the average inner pressure in the flow path up to the patient is increased.
(2) When it is necessary to quickly exhaust carbon dioxide, i.e., when it is necessary to lower the partial pressure of carbon dioxide (PaO2) in the artery blood, one ventilation amount against the lungs of the patient is increased.
(3) The inherent frequency increasing the ventilation efficiency varies depending of each of the patients X as well as the state of the patient. The ventilation frequency is regulated so that the frequency is near the inherent frequency.
The ventilation frequency, at the initial stage, is determined according to the weight of the patient, and then adjusted to a frequency at which resonance is generated with the body of the patient X to increase the gas (oxygen) diffusion efficiency and the gas exchange (between oxygen and carbon dioxide) is effectively performed. In general, the ventilation frequency is set to about 15 {Hz] for a new-born baby and 3 to 10 {Hz] for a child or a grown-up.
During an artificial respiration, the ventilation frequency is normally fixed unless a sudden change is caused in the state of the patient X. The ventilation frequency is not often changed. Accordingly, normally, in order to perform a desired artificial respiration according to the state of the patient X, the respiration state is adjusted with the parameter (1) or (2).
In the aforementioned conventional high-frequency oscillation artificial respiration apparatus 200, the oscillating air pressure amplitude is increased by using a blower 205 having a large output, thus enabling to obtain a sufficient ventilation for lungs of a grown-up. FIG. 17 graphically shows an inner pressure change in the vicinity of the three-way branching pipe 202 during a high-frequency oscillation artificial respiration.
However, in the oscillating air pressure urging unit 203 of the aforementioned conventional high-frequency oscillation artificial respiration apparatus 200, the inner pressure amplitude (difference between the uppermost pressure and the lowermost pressure) in the vicinity of the three-way branching pipe 202 during a high-frequency oscillation artificial respiration exceeds 100 [cm H2O] (9800 [Pa]) and accordingly, it is necessary to carefully adjust the pressure for a patient.
The pressure applied to lungs of a human being is a load to the lungs if the pressure is too high or too low. In the conventional example, the pressure amplitude is increased to perform a sufficient ventilation, which means that the pressure approaches the uppermost or the lowermost pressure. In order to perform a high-frequency oscillation artificial respiration without applying a load to the lungs of a patient, it is necessary to set the pressure with a great care.
Moreover, in the aforementioned high-frequency oscillation artificial respiration apparatus 200, even when the pressure is in a range not applying a load to a patient, a high-frequency oscillation artificial respiration with a large pressure amplitude causes a large vibration of the breast of the patient X, which is not preferable when a medical instrument of instillation or a catheter is applied to the patient X or when a measurement is to be performed using a measurement apparatus.
Furthermore, when the pressure amplitude is increased in the high-frequency oscillation artificial respiration apparatus 200, there arises a problem that the oscillating air pressure urging unit 203 causes a large noise and the power consumption is also increased.
Moreover, there is a case that the patient state is suddenly changed, resulting in an excessive decrease or increase of PaO2. In such a case, the inherent frequency of the patient X has been changed and the adjustments of (1) and (2) alone are insufficient. The ventilation frequency should be changed.
However, when the ventilation frequency is changed, the oscillating flow state in the in-trachea tube is remarkably changed, which in turn changes the gas exchange effect by the patient, causing a further change in the patient. Especially at the ventilation frequency 3 to 10 {Hz] used for a child to a grown-up, a change of 1 [Hz] may remarkably change the gas convey mechanism and the doctor should be very careful when changing the ventilation frequency.
As has been described above, in the conventional high-frequency oscillation artificial respiration apparatus, the xe2x80x9cone ventilation amountxe2x80x9d and the xe2x80x9cventilation frequencyxe2x80x9d represent parameters affecting the partial pressure of carbon dioxide in the artery blood. That is, one cure index is affected by two factors and the high-frequency oscillation artificial respiration apparatus should be operated very carefully. For the doctor using the high-frequency oscillation artificial respiration apparatus, the xe2x80x9csetting of the ventilation frequencyxe2x80x9d is a very complicated operation.
Doctors want a high-frequency oscillation artificial respiration apparatus capable of adjusting the ventilation frequency without causing a sudden change in the partial pressure of carbon dioxide in the artery blood of the patient.
It is therefore an object of the present invention to provide a high-frequency oscillation artificial respiration apparatus capable of performing a sufficient ventilation while reducing the pressure amplitude.
Moreover, an object of the present invention to provide a high-frequency oscillation (hereinafter, referred to as HFO) artificial respiration apparatus in which adjustment can be made without causing interactions between the aforementioned parameters.
The high-frequency oscillation artificial respiration apparatus disclosed in claim 1 comprises: an inhale gas introduction block for supplying an inhale gas containing oxygen to a patient, a patient side path for guiding the inhale gas from the inhale gas introduction block into the patient, an oscillating air pressure urging block for applying an oscillating air pressure having a higher frequency than a respiration frequency of the patient, to the inhale gas flowing through the patient side path, and an exhaust path for exhausting an exhale gas containing carbon oxide exhaled from the patient, into the atmosphere.
Furthermore, the patient side path includes a branching pipe for branching a flow from the inhale gas introduction block to the side of the exhaust path and the side of the patient and an in-trachea insert tube which is connected to the patient side end of the branching pipe and can be inserted through a mouth into lungs of the patient.
The apparatus further comprises an auxiliary inhale gas supply block for supplying an inhale gas up to the vicinity of the lungs of the patient through a path different from the patient side path. The auxiliary inhale gas supply block includes an inhale gas supply source and an auxiliary inhale gas supply path, which is different from the patient side path, for guiding the inhale gas from the supply source into the lungs of the patient.
In the aforementioned configuration, an inhale gas is generated from the inhale gas introduction block and set to a patient through the patient side path. Furthermore, the inhale gas flowing through the patient side path is urged by the oscillating air pressure urging unit. The inhale gas is divided by the branching pipe into the patient side path and the exhaust path. The inhale gas introduced into the patient side is driven by the positive pressure of the oscillating air pressure through the in-trachea insert tube to reach lungs of the patient, thus supplying oxygen to the lungs. On the other hand, an exhale gas containing carbon dioxide is driven by a negative pressure of the oscillating air pressure to flow through the in-trachea insert tube to the branching pipe and is pushed together with a subsequent inhale gas into the exhaust path to be exhausted into the atmosphere.
While the aforementioned ventilation is performed in the lungs, the auxiliary inhale gas supply block supplies an inhale gas from the inhale gas supply source through the auxiliary inhale gas supply path into the lungs of the patient. This auxiliary inhale gas supply path is separated from the patient side path and the gas is not urged by the oscillating air pressure. Moreover, the auxiliary inhale gas supply path is not connected to the exhaust path, either. Accordingly, the inhale gas is supplied slowly at a constant flow rate into the lungs. Accordingly, the exhale gas generated in the lungs is forced to be sent through the in-trachea insert tube into the exhaust path apart form the function of the negative pressure of the oscillating air pressure.
Moreover, the high-frequency oscillation (HFO) artificial respiration apparatus claimed in claim 12 comprises: an inhale gas introduction block for supplying an inhale gas containing oxygen to a patient; a patient side path for guiding the inhale gas from the inhale gas introduction block to the patient; an oscillating air pressure urging block for urging the inhale gas flowing in the patient side path with an oscillating air pressure having a cycle shorter than a respiration cycle of the patient; an exhaust path for exhausting into the atmosphere an exhale gas containing carbon dioxide exhaled from the patient; and a controller for controlling operation of the oscillating air pressure urging block.
The oscillating air pressure urging block can regulate a ventilation amount per oscillation cycle and an oscillating frequency of the oscillating air pressure. Moreover, the controller includes an entry block for accepting the oscillation frequency entered, and an operation control block for controlling the oscillating air pressure urging block to supply an output oscillating air pressure set to the oscillation frequency entered.
The operation control block has a ventilation state maintaining function for modifying the oscillation frequency according to an entered value in such a manner that a ventilation amount per oscillation cycle and an oscillation frequency of the oscillating air pressure are modified while maintaining a value of VT2xe2x80xa2f constant wherein VT represents a ventilation amount per oscillation cycle for lungs of the patient and f represents an oscillation frequency.
In the aforementioned configuration, an inhale gas is generated from the inhale gas introduction block and sent through the patient side path to the patient. Furthermore, the inhale gas flowing in the patient side path is urged by an oscillating air pressure from the oscillating air pressure urging block. The inhale gas is divided in a branching pipe to a patient side and an exhaust path side. The inhale gas flowing into the patient side is sent by the positive pressure of the oscillating air pressure through an in-trachea insert tube to reach the lungs of the patient, thus supplying oxygen to the lungs. Moreover, an exhale gas containing carbon dioxide generated from the lungs is caused by the negative pressure of the oscillating air pressure to flow through the in-trachea insert tube to the branching pipe and pushed together with a subsequent inhale gas into the exhaust path to be exhausted into the atmosphere.
When the ventilation efficiency of the patient is found to be low or the patient state has changed and the oscillation frequency should be set to a new value, the user (doctor) enters a new oscillation frequency value to the entry block through an external input unit connected to the entry block.
The operation control block stars an operation control to modify the oscillation frequency of the oscillating air pressure output from the oscillating air pressure urging block. That is, the oscillating air pressure urging block is regulated to be modified from the previous oscillation frequency to the oscillating frequency entered, upon this modification, the ventilation amount per oscillation cycle is also modified according to the modification of the oscillation frequency. That is, control is performed to modify the oscillation frequency f and the ventilation amount per oscillation cycle so that the one ventilation amount VT for the lungs of the patient and the oscillation frequency f satisfy the condition VT2xe2x80xa2f=constant.
It should be noted that the aforementioned xe2x80x9cventilation amount per oscillation cyclexe2x80x9d represents an oscillation amount per one oscillation cycle of the oscillating air pressure directly output from the oscillating air pressure urging block, and the xe2x80x9cone ventilation amount for lungs of the patientxe2x80x9d represents a ventilation amount actually ventilated per oscillation cycle by the oscillating air pressure which has reached the lungs of the patient.
The xe2x80x9cventilation amount per oscillation cyclexe2x80x9d and the xe2x80x9cone ventilation amount for lungs of the patientxe2x80x9d may not coincide with each other but they change with a steady interrelationship between them. Accordingly, when the target xe2x80x9cone ventilation amount for lungs of the patientxe2x80x9d is known in advance, a corresponding xe2x80x9cventilation amount per oscillation cyclexe2x80x9d can be identified. The operation control of the oscillating air pressure urging block is performed so as to obtain the target xe2x80x9cventilation amount per oscillation cyclexe2x80x9d.
The present invention achieves the aforementioned object by the aforementioned configuration.